The role of membrane phosphorylation in the regulation of cell and membrane functions will be studied in the human erythrocyte which has a membrane-associated protein kinase. The working hypothesis for this proposal suggests that changes in state of phosphorylated membrane components produce changes in erythrocyte membrane structure and function in a series of steps. After phosphorylation there is a change and/or translocation of membrane-bound calcium. This may soon be followed or associated with a change in ion permeability as well as membrane-associated enzymes. This may be reflected in a change in overall membrane structure and function as well as erythrocyte functions, e.g., glycolysis and oxygen transport by hemoglobin. Each change in state of a phosphorylated membrane component will be studied kinetically and stoichiometrically to establish the sequence of membrane and cell reactions.